This application claims the benefit of Korean Application No. 2001-48363, filed Aug. 10, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus to adjust a head gap of an ink-jet printer, and more particularly, to an apparatus to smoothly adjust a head gap of an ink-jet printer.
2. Description of the Related Art
As shown in FIG. 1, a general ink-jet printer has a carriage 3 which moves along a shaft 2 disposed at a main frame 1. The shaft 2 has an eccentric supporting shaft 2a to vary a position of the carriage 3 up and down during a rotation thereof. Being supported by a conveying belt 5 rotated by a motor 6, the carriage 3 reciprocates longitudinally along the shaft 2. The carriage 3 includes an ink cartridge 4 and a head 4a. The head 4a allows ink in the ink cartridge 4 to jet to paper xe2x80x98P,xe2x80x99 which passes underneath the ink cartridge 4, to print a predetermined image on the paper xe2x80x98P.xe2x80x99
A head gap adjusting means is provided to adjust a gap between the head 4a and the paper xe2x80x98P.xe2x80x99 The head gap adjusting means adjusts a position of the shaft 2 to maintain the head gap xe2x80x98Gxe2x80x99 according to the thickness of the provided paper xe2x80x98P.xe2x80x99 The head gap adjusting means includes a worm wheel gear 7 connected to the supporting shaft 2a, a worm gear 8 drivedly connected to the worm wheel gear 7, and a motor 9 for driving the worm gear 8. The worm wheel gear 7 is connected to the supporting shaft 2a and rotates in association with the worm gear 8.
In the state shown in FIG. 2A, the head gap xe2x80x98Gxe2x80x99 must be increased when paper xe2x80x98Pxe2x80x99 of a greater thickness is supplied. In order to increase the head gap xe2x80x98G,xe2x80x99 the worm gear 8 and the worm wheel gear 7 are rotated in a direction indicated by arrow xe2x80x98Axe2x80x99 by a driving force of the motor 9. Then, the worm wheel gear 7 rotates until a stopper 7a, formed on the worm wheel gear 7 is stopped at a protrusion 1a formed on a predetermined portion of the main frame 1. Then, the motor 9 is forcedly driven for a predetermined time in the state in which the stopper 7a is stopped at the protrusion 1a. As a result, the motor is stopped due to a driving load, as shown in FIG. 2B.
On the other hand, in order to reduce the head gap xe2x80x98G,xe2x80x99 the worm wheel gear 7 is rotated in a direction indicated by arrow xe2x80x98Bxe2x80x99, as shown in FIG. 2B. The motor 9 is driven until the stopper 7a is stopped at another protrusion 1b, and then the motor 9 is forcedly stopped due to the driving load. Then, as shown in FIG. 2A, a center of the shaft 2, which is eccentric with respect to the supporting shaft 2a, descends such that the head gap xe2x80x98Gxe2x80x99 is reduced.
According to the conventional construction as described above, the motor 9 is continuously driven for a predetermined time even after the worm wheel gear 7 is stopped at the protrusions 1a and 1b. Thus, there is a problem in that gear teeth between the worm gear 8 and the worm wheel gear 7 are dislocated, thereby causing a malfunction. Furthermore, if the worm wheel gear 7 is continuously rotated in a different direction with the dislocated gear teeth, smooth operation is not achieved.
Meanwhile, in another example of a conventional construction, the motor 9 includes an on/off switch, which is controlled to be on/off in accordance with a rotating position of the worm wheel gear 7. Thus, the switch controls the driving of the motor 9. However, there is a problem of an increased cost of installing the on/off switch.
Accordingly, it is an object of the present invention to solve the above problems.
It is a further object of the present invention to provide an apparatus to smoothly adjust a head gap of an ink-jet printer.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing an apparatus to adjust a head gap of an ink-jet printer, including a main frame; a main shaft rotatably disposed at the main frame and having an eccentric supporting shaft; a head assembly movably disposed on the main shaft and having a head to provide ink to a printing medium to print an image thereon; a motor to provide a driving force to rotate the main shaft; a worm wheel connected to the eccentric supporting shaft to rotate in association with the eccentric supporting shaft; a rotation angle control unit to restrict a rotation angle of the worm wheel to restrict a range of the head gap, the head gap being between the head and the printing medium; and a clutch unit to selectively transmit the driving force of the motor to the worm wheel and to prevent a transmission of the driving force from the motor to the worm wheel when the worm wheel is restricted by the rotation angle control unit.